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Scientists performed unprecedented tests on the pod of stranded orcas near Tuatapere yesterday.

They had hoped to take samples that would help solve the mystery behind the beaching and death of the pod of nine near Blue Cliffs on Tuesday night.

By the time researchers arrived, one carcass had been washed away, another partly eaten by sharks and the remaining seven were severely decomposed.

Wildbase pathologist Stuart Hunter said tests yesterday would not be able to determine the cause of death. "They are too far decomposed," he said.

He had hoped to be able to take blood tests that could determine whether the orcas had died from an infection or disease.

"By the time the skin starts peeling off like it has here it is too late." Mr Hunter believed blood tests would still be useful in determining whether pollution or heavy metals had a role in the orcas' deaths.

Researchers took measurements and blubber samples of the mammals to, hopefully, determine age, sex and condition.

Orca Research Trust founder Ingrid Visser said the animals when living were in very good condition.

"I don't know any of them, which is good but sad because where have they come from?"

Initial observation of their teeth resembled a pod in the northern Pacific region that fed predominantly on sharks.

"It could be very possible that they were hunting sharks in shallow water."

Dr Visser said she would take stomach content samples to investigate the theory further.

"There is still so much unknown, we will send tests back to Massey University and potentially overseas," she said.

"A lot of people are thinking that the stranding is possibly linked to seismic activities, earthquakes, in the area, but it is hard to determine." Dr Visser had unprecedented access to the orcas and hopes to uncover more about the pod's behaviour and life.